Human milk sugars fight deadly bacteria

Human milk is a combination of fats, sugars and proteins that changes day to day. Researchers have previously focused on the protective qualities of the proteins but in the new study scientists found the sugars have not only antibacterial properties, but qualities that boost the antibacterial effectiveness of proteins as well.

Said study lead Steven Townsend: “This is the first example of generalized, antimicrobial activity on the part of the carbohydrates in human milk…. One of the remarkable properties of these compounds is that they are clearly non-toxic, unlike most antibiotics.”

In their quest for insights, Townsend and team were motivated by the growing problem of antibiotic resistance in bacteria, which the U.S. government estimates is responsible for about 23,000 deaths each year. “We started to look for different methods to defeat infectious bacteria,” Townsend said. “We turned to one particular bacteria, Group B Strep. We wondered whether its common host, pregnant women, produces compounds that can either weaken or kill strep, which is a leading cause of infections in newborns worldwide.” Rather than proteins in human milk, the Vanderbilt teams looked at the antimicrobial properties of the harder to study sugars.

The team collected human milk carbohydrates, also known as oligosaccharides, and profiled them using mass spectrometry. This can identify thousands of big biomolecules at once. They then introduced the compounds strep cultures. Under a microscope they found the sugars not only killed bacteria, but disintegrated the biofilm strep uses to protect itself.

Out of five samples collected, Townsend found one killed most of an entire colony of strep. Another sample was moderately effective, while the remaining thress showed low levels of antimicrobial activity.

Said Townsend: “Our results show that these sugars have a one-two punch…. First, they sensitize the target bacteria and then they kill them. Biologist sometimes call this ‘synthetic lethality’ and there is a major push to develop new antimicrobial drugs with this capability.”

In supporting studies, the researchers discovered the milk sugars’ antimicrobial qualities successfully countered two of the six so-called “ESKAPE” pathogens that are the leading cause of hospital infections worldwide.

The results were published in Infectious Diseases journal on Jun. 1 in a paper titled, “Human Milk Oligosaccharides Exhibit Antimicrobial and Anti-Biofilm Properties Against Group B. Streptococcus.”